A nuclear and radiation accident is defined by the International Atomic agency as an “event that has led to significant consequences to people, the environment or the facility”. Examples include lethal effects to individuals, large radioactivity release to the environment, or “reactor core melt.”
The prime example of a “major nuclear accident” is one in which a reactor core is damaged and significant amounts of radiation are released, such as in the Chernobyl Disaster in 1986. The impact of nuclear accidents has been a topic of debate practically since the first nuclear reactors were constructed. It has also been a key factor in public concern about nuclear facilities.
Some technical measures to reduce the risk of accidents or to minimize the amount of radioactivity released to the environment have been adopted. Despite the use of such measures, “there have been many accidents with varying impacts as well near misses and incidents”.
Benjamin K. Sovacool has reported that worldwide there have been 99 accidents at nuclear power plants. Fifty-seven accidents have occurred since the Chernobyl disaster, and 57% (56 out of 99) of all nuclear-related accidents have occurred in the USA.
Serious nuclear power plant accidents include the Fukushima Daiichi nuclear disaster (2011), Chernobyl disaster (1986), Three Mile Island accident (1979), and the SL-1 accident (1961). Stuart Arm states, “apart from Chernobyl, no nuclear workers or members of the public have ever died as a result of exposure to radiation due to a commercial nuclear reactor incident.”
Nuclear-powered submarine mishaps include the K-19 reactor accident (1961), the K-27 reactor accident (1968), and the K-431 reactor accident (1985). Serious radiation accidents include the Kyshtym disaster, Wind scale fire, radiotherapy accident in Costa Rica, radiotherapy, and radiation accident in Morocco, Goiania accident, radiation accident in Mexico City, radiotherapy unit accident in Thailand, and the Mayapuri radiological accident in India.
Two of the major nuclear accidents are as follows:
(i) Chernobyl Nuclear Disaster:
26th of April 1986 witnessed one of the world’s worst Nuclear Disaster ever in Chernobyl. Chernobyl is approximately 80 miles (which is 120 kilometers) north of the capital city of the Ukraine, Kiev. The accident took lives of 30 people immediately and vast evacuation of 135000 people within 20 mile radius of the power plant was carried out after the accident.
Causes of the Accident:
There was not one cause of this accident, there were several which all contributed to it. This accident happened while testing an RMBK reactor. A chain reaction occurred in the reactor and got out of control, causing explosions and a huge fireball which blew off the heavy concrete and steel lid on the reactor.
These are the causes:
- Design fault in RBMK reactor
- A violation, of procedures
- Breakdown of communication
- Lack of a ‘Safety Culture’ in the power plant
Consequences of the Accident:
1. Environmental consequences:
The radioactive fallout caused radioactive material to deposit itself over large areas of ground. It has had an effect over most of the northern hemisphere in one way or another. In some local ecosystems within a 6 mile (10 km) radius of the power plant the radiation is lethally high especially in small mammals such as mice and coniferous trees. Luckily within 4 years of the accident nature began to restore itself, but genetically these plants may be scarred for life.
2. Health effects:
Firstly, there was a huge increase in Thyroid Cancer in Ukrainian children (from birth to 15 years old). From 1981-1985 there was an average of 4-6 patients per million but between 1986 and 1997 this increased to an average of 45 patients per million.
It was also established that 64% of Thyroid Cancer patients lived in the most contaminated areas of the Ukraine (Kiev province, Kiev city, provinces of Rovno, Zhitomir, Cherkassy and Chernigov).
3. Psychological consequences:
There has been an increase in psychological disorders such as anxiety, depression, helplessness and other disorders which lead to mental stress. These disorders are not a consequence of radiation, but a consequence from the stress of evacuation, the lack of information given after the accident and the stress of knowing that their health and their children’s health could be affected.
4. Economic, political and social consequences:
The worst contaminated areas were economically, socially and politically declining as the birth rate had decreased and emigration numbers had substantially risen which had caused a shortage in labour force. These areas could not evolve industrially or agriculturally because of strict rules that were introduced because the area was too contaminated.
The few products made were hard to sell or export because people were aware that it had come from the Ukraine and so were scared of being affected, this caused a further economic decline. Socially people have been limited on their activities making everyday life very difficult.
Now in the year 2000, everything is looking a lot better and is starting to rise again and probably in about 10 years time almost everything will be as good as normal in the Ukraine.
(ii) Fukushima Daiichi Nuclear Disaster:
The Fukushima Daiichi nuclear disaster was a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the Tohoku earthquake and tsunami on 11 March, 2011. It is the largest nuclear disaster since the Chernobyl disaster of 1986.
The plant comprises six separate boiling water reactors originally designed by General Electric (GE), and maintained by the Tokyo Electric Power Company (TEPCO). At the time of the quake, Reactor 4 had been de-fuelled while 5 and 6 were in cold shutdown for planned maintenance.
The remaining reactors shut down automatically after the earthquake, and emergency generators came online to control electronics and coolant systems. The tsunami resulted in flooding of the rooms containing the emergency generators.
Consequently those generators ceased working, causing eventual power loss to the pumps that circulate coolant water in the reactor. The pumps then stopped working, causing the reactors to overheat due to the high decay heat that normally continues for a short time, even after a nuclear reactor shut down.
The flooding and earthquake damage hindered external assistance. In the hours and days that followed. Reactors 1, 2 and 3 experienced full meltdown. As workers struggled to cool and shut down the reactors, several hydrogen- air chemical explosions occurred.
The hydrogen gas was produced by high heat in the reactors causing a hydrogen-producing reaction between the nuclear fuel metal cladding and the water surrounding them. The government ordered that seawater be used to attempt to cool the reactors this had the effect of ruining the reactors entirely. As the water levels in the fuel rods pools dropped, they began to overheat. Fears of radioactivity releases led to a 20 km (12 mi)-radius evacuation around the plant.
During the early days of the accident workers were temporarily evacuated at various times for radiation safety reasons. Electrical power was slowly restored for some of the reactors, allowing for automated cooling.